Effects of insulator charging on surface breakdown in vacuum

Insulator charging is correlated with the flashover phenomenon but it was difficult to determine if the charge was the cause or the consequence of the flashover. This was achieved in two steps including: (1) the investigation of charging effects produced under various type of stresses (electron bombardment, mechanical, electrical); (2) the development of a new method to produce and to investigate the mechanism, of surface breakdown in vacuum. The author has shown that the complex dielectric constant of the insulator is the key parameter which dictates the breakdown characteristics. A fast change of the polarization of the dielectric is believed to be responsible for initiation of a plasma which expands on the surface with treeing